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Monday, August 16, 2010

A new startup company will attempt to solve the biggest roadblock facing electric vehicles today--the cost of their batteries.

The new company, called 24M, has been spun out of the advanced battery company A123 Systems. It will develop a novel type of battery based on research conducted by Yet-Ming Chiang, a professor of materials science at MIT and founder of A123 Systems. He says the battery design has the potential to cut those costs by 85 percent.

The new company has raised $10 million in venture-capital funding, and about $6 million from the Advanced Research Projects Agency-Energy (ARPA-E), which will fund collaboration between the company and MIT and Rutgers University. A123 Systems will work closely with the new company, and owns stock in it. The name stands for "24 molar," referring to material concentration levels that Chiang cryptically calls "technically significant" to the company.

Chiang isn't saying much about the details of the new battery--such as exactly what materials it's made of. But he does say that it uses a "semisolid" energy storage material (rather than the solid electrode material used in most batteries today), and that it combines the best attributes of conventional batteries, fuel cells, and something called flow batteries, while avoiding some of the disadvantages of these technologies.

One advantage of lithium-ion batteries--the kind used in laptops, and which will be used in a new wave of electric vehicles coming out starting at the end of the year--is that the electrode materials can store large amounts of energy. But the packaging required to handle that energy takes up a lot of space and adds cost and weight. "In a typical rechargeable battery, only half of it is actual energy-storing materials. The rest is supporting materials," Chiang says. "That's a problem I've been thinking about for years--how do you improve the efficiency of the design?"

Reducing the amount of materials isn't easy. To extract useful amounts of electric current from electrode materials, these materials have to be spread in very thin layers over sheets of foil, which take up a lot of volume inside the cell.

Fuel cells and flow batteries don't have this problem. The energy-storing material--a fuel such as hydrogen or a liquid electrolyte, respectively--can be flowed past a membrane, which makes it easier to get the energy out.

The problem with a fuel cell is that it can't be recharged by applying electrical current--you need to refill the fuel tank. That's fine if the fuel is widely available, but right now hydrogen can be hard to come by. Flow batteries require vast amounts of electrolyte because their energy density is low. "It's like managing a swimming pool full of corrosive liquid," Chiang says. As a result, flow batteries are not practical for cars.

As with fuel cells, the new battery can store large amounts of energy without also needing large amounts of supporting materials to extract it, Chiang says. Yet it retains the rechargeability and energy density of lithium battery electrode materials. The result is that the battery can store a relatively large amount of energy at low cost. But he's purposefully vague about the mechanisms involved, saying only, "The final version of the device will look very different from both a conventional battery and a flow battery."

Chiang says the new design could work with a range of battery chemistries. So far, he's developed a proof-of-concept device--which was needed to get the Arpa-e grant. But, he says, "there's a lot of work to do." He's setting a goal of five years to get the first systems out in the field.